Ovulation Calculator UK
Find your fertile window and peak ovulation day. Enter the first day of your last period and your average cycle length to see your best days to conceive.
Just starting out? Read our full trying to conceive guide for tips on timing, fertility and when to see your GP.
Enter the first day of your last period and your average cycle length to find your fertile window.
How does ovulation work?
Ovulation is when a mature egg is released from the ovary. It typically occurs around 14 days before your next period starts. If you have a regular 28-day cycle, ovulation usually happens around day 14. For longer or shorter cycles, the timing shifts.
The fertile window lasts approximately six days: the five days before ovulation and the day of ovulation itself. Sperm can survive in the reproductive tract for up to five days, so having sex in the days leading up to ovulation gives you the best chance of conceiving.
The three days with the highest chance of conception are the two days before ovulation and the day of ovulation itself. This is sometimes called the "peak fertile days." For a wider set of tips for trying to conceive, including lifestyle and partner factors, see our dedicated guide. Once you have ovulated, our guide on earliest test date after ovulation explains when a pregnancy test becomes reliable, and once you get a positive you can calculate your due date once pregnant.
Signs of ovulation
Change in cervical mucus
Around ovulation, discharge becomes clear, slippery and stretchy (like raw egg white).
Slight rise in basal body temperature
Your resting temperature rises by about 0.2 to 0.5 degrees Celsius after ovulation.
Mild pelvic pain (Mittelschmerz)
Some people feel a brief twinge or cramp on one side of the lower abdomen.
Increased libido
Many people notice a natural increase in sex drive around their fertile days.